N-acyl acidic amino acid or salt thereof is a kind of compound prepared from acylated amino acid. Typically, it is made by condensing fatty acid chloride and amino acid. Such kind of compound has good surface activity, foaming performance, cleaning performance and mildness, and therefore, it is widely used in cosmetics, personal care cleansing products, and meanwhile, it also has a wide range of application in other fields, such as food additives, metal machining, ore floatation, oil and gas mining, as well as agriculture, biological products and pharmaceutical preparation.
N-acyl acidic amino acid or salt thereof is a compound made by acylating such acidic amino acids as glutamic acid and aspartic acid, such that it embodies higher performance than acylated neutral amino acid products. Glutamic acid surfactants have better application characteristics than neutral amino acid surfactants, such as better foams, suitability to be used in weakly acidic system, matching with human skin pH, and even less irritation, etc. Typically, N-acyl acidic amino acid or salt thereof are made by condensing fatty acid chloride and amino acid. Such production process uses a lot of solvents, such as polar solvents as acetone, methyl ethyl ketone, dioxane, tetrahydrofuran, etc. In the present industrial production, water has already been used as solvent for the neutral amino acid surfactants, such that it can substantially reduce cost. Such products have already been widely used. However, when water is used as solvent in the condensation reaction of acidic amino acid with fatty acid chloride, the conversion ratio is relative low, normally 70%. In addition, such products have low quality, and subject to complicated post treatment. In actual production, it often uses polar organic solvents, such that the conversion ratio can be substantially increased to 85% to 90%. But it has the problem of complicated post treatment and increased cost, which makes it difficult to be used as widely as neutral amino acid surfactants.
U.S. Pat. No. 6,008,390 discloses that in the water-phase reaction system, conversion ratio of glutamic acid can be increased to about 85% with high power agitator. But this process causes power consumption to increase substantially. In addition, it is very difficult to enlarge large scale industrialized production equipment. High speed agitator may also produce too much foam, which reduces reaction and mixing effect. All these factors undoubtedly bring difficulty to production and increase production cost, and therefore hinder the market application. In addition, in the above preparation process, too much excess amount of glutamic acid, high cost, and residual amino acid in the product all bring problems to the usage.